A variety of implantable medical devices have been proven to be effective for treatment of a variety of diseases. Many of such devices, such as cardiac pacemakers, defibrillators, spinal cord or deep brain stimulators, gastric stimulators, and the like, employ accessory medical leads to deliver electrical signals from a signal generating device to tissue of a patient at a location removed from the signal generating device. Typically the lead is tunneled from a subcutaneous region of the patient in which the signal generating device is implanted to a target tissue location. It is often important that the lead, or portions thereof, does not shift or move once implanted to ensure that a therapeutic signal continues to be delivered to the target tissue. One mechanism for retaining the implanted position of a lead or portion thereof is the use of tines. The tines or other fixation elements are typically attached to various locations of the lead and are deployed once the lead is properly positioned in the patient. Most often, tines or other fixation elements prevent retrograde movement of the lead. Once the fixation elements are deployed, it can be difficult to change the position of the lead.
Prior to deploying the fixation elements, it is often desirable to apply electrical signals to the patient via electrodes of the lead, as the lead is being implanted, to determine whether the lead is being positioned in an appropriate location or if the tract of implantation is proceeding in a desired direction. This process is sometimes referred to a trolling, where test electrical signals are applied as the lead is advanced to aid in the proper placement of the lead. However, with the use of standard lead introducer devices, it is not possible to perform such trolling when the self-expanding fixation elements are disposed on the lead distal to the electrodes. That is, absent fixation elements being distal electrodes of the lead, the lead may extended distally beyond the introducer (or the introducer may be withdrawn to expose the distal end of the lead) such that a test electrical signal may be delivered to the patient via electrodes of the lead, and the lead may be withdrawn into the introducer (or introducer advanced) and repositioned. This process may be repeated until the lead is determined to be in an appropriate location, and the introducer may be completely withdrawn. However, when the fixation elements are disposed on the lead distal to the electrodes, the fixation elements will be deployed during the initial test stimulation (when extended beyond the distal end of the introducer), and the ability to reposition the lead will be compromised, if not lost.